Class Of Solid Electrolytes Research Articles

Garnet-Type Zinc Hexacyanoferrates as Lithium, Sodium, and Potassium Solid Electrolytes

Sodium-ion batteries offer an attractive alternative to lithium-based chemistries due to the lower cost and abundance of sodium compared to lithium. Using solid electrolytes instead of liquid ones in such batteries may help improve safety and energy density, but they need to combine easy processing with high stability toward the electrodes. Herein, we describe a new class of solid electrolytes that are accessible by room-temperature, aqueous synthesis. The materials exhibit a garnet-type zinc hexacyanoferrate framework with large diffusion channels for alkaline ions. Specifically, they show superionic behavior and allow for facile processing into pellets. We compare the structure, stability, and transport properties of lithium-, sodium-, and potassium-containing zinc hexacyanoferrates and find that Na2Zn3[Fe(CN)6]2 achieves the highest ionic conductivity of up to 0.21 mS/cm at room temperature. In addition, the electrochemical performance and stability of the latter solid electrolyte are examined in solid-state sodium-ion batteries.

Design of a trigonal halide superionic conductor by regulating cation order-disorder.

Lithium-metal-halides have emerged as a class of solid electrolytes that can deliver superionic conductivity comparable to that of state-of-the-art sulfide electrolytes, as well as electrochemical stability that is suitable for high-voltage (>4 volt) operations. We show that the superionic conduction in a trigonal halide, such as Li3MCl6 [where metal (M) is Y or Er], is governed by the in-plane lithium percolation paths and stacking interlayer distance. These two factors are inversely correlated with each other by the partial occupancy of M, serving as both a diffusion inhibitor and pillar for maintaining interlayer distance. These findings suggest that a critical range or ordering of M exists in trigonal halides, and we showcase the achievement of high ionic conductivity by adjusting the simple M ratio (per Cl or Li). We provide general design criteria for superionic trigonal halide electrolytes.

Compositionally complex perovskite oxides: Discovering a new class of solid electrolytes with interface-enabled conductivity improvements

Compositionally complex perovskite oxides: Discovering a new class of solid electrolytes with interface-enabled conductivity improvements

Stabilizing the Halide Solid Electrolyte to Lithium by a β-Li3N Interfacial Layer.

As a new class of solid electrolytes, halide solid electrolytes have the advantages of high ionic conductivity at room temperature, stability to high-voltage cathodes, and good deformability, but they generally show a problem of being unstable to a lithium anode. Here, we report the use of Li3N as an interface modification layer to improve the interfacial stability of Li2ZrCl6 to the Li anode. We found that commercial Li3N can be easily transformed into an α-phase and a β-phase by ball-milling and annealing, respectively, in which β-phase Li3N simultaneously has high room-temperature ionic conductivity and good stability to both Li and Li2ZrCl6, making it a good choice for an artificial interface layer material. After the modification of the β-Li3N interfacial layer, the interfacial impedance between Li2ZrCl6 and the Li anode decreased from 1929 to ∼400 Ω. At a current density of 0.1 mA cm-2, the overpotential of the Li symmetric cell decreased from 250 to ∼50 mV, which did not show an obvious increase for at least 300 h, indicating that the β-Li3N interface layer effectively improves the interfacial stability between Li2ZrCl6 and Li.

Solid electrolyte based on 2-adamantanone for all-solid-state lithium-ion batteries

Solid-state batteries are considered the next step in battery technology. Materials investigated for application as solid-state electrolytes are mainly oxide ceramics, sulfidic (glass-) ceramics, and polymers. Besides these, another class of solid electrolytes with promising properties is based on plastic crystals. Especially due to their waxy behavior, they promise good interfaces within a solid-state battery. In this work, a new plastic crystal, 2-adamantanone, is investigated as basis for a solid electrolyte for the first time. Its large temperature window from − 95 to 255 °C for its plastic (conductive) state and the high dipole moment of 3.4 D make it a promising material for battery application. The mixture with a lithium salt was investigated thermally with TGA and DSC revealing stability in a large temperature range from − 30 to + 80 °C. IR investigations show the dissociation of the conductive salt, which is necessary for the lithium ion conduction. The ionic conductivity of the electrolytes reaches values up to 1.4·10−4 S/cm at room temperature with a very low activation energy of only 0.32 eV.

Investigating the Effects of Lithium Phosphorus Oxynitride Coating on Blended Solid Polymer Electrolytes

Solid state electrolytes are very promising to enhance the safety of lithium ion batteries. Two classes of solid electrolytes, polymer and ceramic, can be combined to yeild a hybrid electrolyte that can syngergistically combine the properties of both materials. Chemical stability, thermal stability, and high mechanical moduli of ceramaic electrolytes against dendrite penetration can be combined with the flexibility and ease of processing of polymer electrolytes. By laminating a polymer electrolyte with a ceramic electrolyte, the stability of the solid electrolyte is expected to improve against lithium metal, and the ionic conductivity could remain close to the value of the original polymer electrolyte as long as an appropriate thickness of the ceramic eletrolyte is applied. Here we report a bilayered lithium-ion conducting hybrid solid electrolyte consisting of a blended polymer electrolyte (BPE) laminated with a thin layer of the inorganic solid electrolyte lithium phosphorous oxynitride (LiPON). The hybrid system was thoroughly studied. First, we investigated the influence of polymer chain length and lithium salt ratio on the ionic conductivity of the BPE based on poly(ethylene oxide) (PEO) and poly(propylene carbonate) (PPC) with the salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The optimized BPE consisted of 100k molecular weight PEO, 50k molecular weight PPC, and 25(w/w) % LiTFSI, (denoted as PEO100PPC50LiTFSI25) which exhibited an ionic conductivity of 2.11x10-5 S/cm, and the ionic conductivity showed no thermal memory effects as the PEO crystallites were well distrupted by PPC and LiTFSI. Secondly, the effects of LiPON coating on the BPE were evaluated as a function of thickness down to 20 nm. The resulting bilayer structure showed an increase in the voltage window from 5.2 to 5.5V (vs Li/Li+) and thermal activation energies that approached the activation energy of the BPE when thinner LiPON layers were used, resulting in similar ionic conductivities for 30nm LiPON coatings on PEO100PPC50LiTFSI25. Coating BPEs with a thin layer of LiPON is shown to be an effective strategy to improve the long-term stability against lithium.

(Keynote) An Automatic Rapid Screening Tool for Fast Ionic Conductors

Identifying new materials that combine high ionic conductivity with structural and electrochemical stability so far remains a slow trial and error search process. To rationally accelerate materials design and exploit the opportunities in the materials genome a dependable rapid screening of materials is required that can pre-select structures that merit higher level computational as well as experimental characterization. Here we report on the progress of our “softBV” bond-valence site energy-based automated pathway analysis utilizing our new Bond Valence Pathway Analyzer (BVPA) – with fast bond valence site energy calculations to quickly obtain suggested candidate materials for fast ionic conduction. BVPA provides rapid and simplified visualization, in order to bridge the gap between experimentalists and simulation [1,2]. Calculation of ion transport pathways can be done extremely quickly on the order of seconds or minutes on desktop PCs providing a speedup factor of 3 to 5 orders of magnitude compared to DFT-based NEB methods. Combined with a graphical user interface our software suite (that can be downloaded from [2] and is free for academic use) should enable experimentalists to quickly identify candidate solid electrolyte materials. We also aim to integrate the pre-screening into an automated workflow for subsequent DFT characterization [3].Results will be benchmarked against both experimental and DFT NEB migration barriers. Besides the migration barriers the approach now also comprises an AI-based dopant predictor utilizing bond-valence-based crystal chemical descriptors to assist experimentalists in exploring favorable substitutional doping strategies. We will also compare the predictability of absolute room temperature conductivities from static energy landscape analysis, bond-valence based empirical MD simulations and ab initio molecular dynamics (AIMD) simulations. While for small fast-ion conductor structures at sufficiently high temperatures AIMD appears to be the gold standard, the less reliable but computationally empirical approaches have an advantage in modelling complex disordered interfaces at low temperatures over longer periods. This eliminates the hazards involved in extrapolations down to room temperature properties for the frequent cases of order-disorder phase transitions at intermediate temperatures.As an example we will discuss lithium and sodium compounds containing multiple anions, in particular the combination of thiophosphate and halide anions or various MS4 polyanions. Based on computational screening using our bond valence site approach and DFT studies several thiophosphate halides along the A3PS4-LiX (Cl, Br, I; A = Li, Na) tie line [4] and the Ax(MS4)y(M’S4)z phase space [5] have been explored and their properties discussed based on BVSE pathway models and molecular dynamics simulations in combination with experimental (X-ray and neutron) diffraction, solid state NMR and electrochemical characterisation. MD simulations e.g. show that Li5(PS4)Cl2 is found to undergo an order-disorder phase transition and thus should, contrasting to earlier predictions, not be a fast Li+ ion conductor. The newly predicted thermodynamically stable cubic solid electrolyte Li15(PS4)4Cl3 was successfully prepared and characterized. Though its conductivity does not reach a superionic level, it demonstrates that the computational approach can successfully predict a completely new classes of solid electrolytes and can predict its optimization by doping. The simplicity of the approach also facilitates the study of homogeneity ranges as exemplified for the solid solution systems Li4-xPS4Ix (0<x<0.67) and Na9+x(MS4)3-x(SnS4)x (M = P, Sb; x ≈ 2).

Protic Ionic Liquids‐Based Crosslinked Polymer Electrolytes: A New Class of Solid Electrolytes for Energy Storage Devices

Protic Ionic Liquids‐Based Crosslinked Polymer Electrolytes: A New Class of Solid Electrolytes for Energy Storage Devices

Investigating the Effects of Lithium Phosphorous Oxynitride Coating on Blended Solid Polymer Electrolytes.

Solid-state electrolytes are very promising to enhance the safety of lithium-ion batteries. Two classes of solid electrolytes, polymer and ceramic, can be combined to yield a hybrid electrolyte that can synergistically combine the properties of both materials. Chemical stability, thermal stability, and high mechanical modulus of ceramic electrolytes against dendrite penetration can be combined with the flexibility and ease of processing of polymer electrolytes. By coating a polymer electrolyte with a ceramic electrolyte, the stability of the solid electrolyte is expected to improve against lithium metal, and the ionic conductivity could remain close to the value of the original polymer electrolyte, as long as an appropriate thickness of the ceramic electrolyte is applied. Here, we report a bilayered lithium-ion conducting hybrid solid electrolyte consisting of a blended polymer electrolyte (BPE) coated with a thin layer of the inorganic solid electrolyte lithium phosphorous oxynitride (LiPON). The hybrid system was thoroughly studied. First, we investigated the influence of the polymer chain length and lithium salt ratio on the ionic conductivity of the BPE based on poly(ethylene oxide) (PEO) and poly(propylene carbonate) (PPC) with the salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The optimized BPE consisted of 100 k molecular weight PEO, 50 k molecular weight PPC, and 25(w/w)% LiTFSI, (denoted as PEO100PPC50LiTFSI25), which exhibited an ionic conductivity of 2.11 × 10-5 S/cm, and the ionic conductivity showed no thermal memory effects as the PEO crystallites were well disrupted by PPC and LiTFSI. Second, the effects of LiPON coating on the BPE were evaluated as a function of thickness down to 20 nm. The resulting bilayer structure showed an increase in the voltage window from 5.2 to 5.5 V (vs Li/Li+) and thermal activation energies that approached the activation energy of the BPE when thinner LiPON layers were used, resulting in similar ionic conductivities for 30 nm LiPON coatings on PEO100PPC50LiTFSI25. Coating BPEs with a thin layer of LiPON is shown to be an effective strategy to improve the long-term stability against lithium.

Anisotropic Elastic Properties of Battery Anodes

Negative battery electrodes based on metals exhibit theoretical energy densities that surpass those of the intercalation-based anodes used in present-day Li-ion batteries. Nevertheless, metal anodes have a propensity to form dendrites during charging; thus, use of interfacial protection schemes or solid electrolytes (SE) may be necessary for these systems to be practical. The efficacy of these schemes are influenced by the interplay of the mechanical properties of the anode with those of the SE. To aid in the design of robust anode/SE interfaces, the present study employs Density Functional Theory calculations to assess the elastic properties of eight candidate anode materials: Li, Na, K, Ca, Mg, Zn, Al, and Si. The elastic constants, Young’s modulus, and shear modulus are predicted as a function of temperature within the quasi-harmonic approximation. Anisotropy is assessed by resolving the moduli as a function of crystallographic direction. The alkali metals (Li, Na, and K) are predicted to have the smallest elastic moduli overall, and their moduli decrease with increasing atomic number. Regarding anisotropic behavior, Al and Mg are predicted to exhibit highly isotropic elastic properties, while the alkali metals are highly anisotropic. In the cubic systems, the crystallographic directions exhibiting extrema in the elastic properties are diametrically opposed: under axial loading the stiffest (most compliant) orientation is 〈111〉 (〈100〉), while in shear 〈100〉 (〈111〉) is the stiffest (most compliant). Importantly, the maximum anisotropic shear modulus of some metals is observed to be more than twice as large as their respective polycrystalline values. In these cases the polycrystalline properties may be a poor approximation to the elastic behavior. Accounting for this anisotropy, the resistance to dendrite initiation of several classes of solid electrolytes is discussed.

Understanding interface stability in solid-state batteries

Solid-state batteries (SSBs) using a solid electrolyte show potential for providing improved safety as well as higher energy and power density compared with conventional Li-ion batteries. However, two critical bottlenecks remain: the development of solid electrolytes with ionic conductivities comparable to or higher than those of conventional liquid electrolytes and the creation of stable interfaces between SSB components, including the active material, solid electrolyte and conductive additives. Although the first goal has been achieved in several solid ionic conductors, the high impedance at various solid/solid interfaces remains a challenge. Recently, computational models based on ab initio calculations have successfully predicted the stability of solid electrolytes in various systems. In addition, a large amount of experimental data has been accumulated for different interfaces in SSBs. In this Review, we summarize the experimental findings for various classes of solid electrolytes and relate them to computational predictions, with the aim of providing a deeper understanding of the interfacial reactions and insight for the future design and engineering of interfaces in SSBs. We find that, in general, the electrochemical stability and interfacial reaction products can be captured with a small set of chemical and physical principles. The reliable operation of solid-state batteries requires stable or passivating interfaces between solid components. In this Review, we discuss models for interfacial reactions and relate the predictions to experimental findings, aiming to provide a deeper understanding of interface stability.

Next Generation of Materials for Lithium-Ion Battery Anodes, Cathodes, Separators & Electrolytes

Energy density and cost of conventional Li-ion batteries (LIBs) are closely approaching their limits. The reliance of conventional cathodes on the use of toxic metals additionally endangers health and safety of miners in developing countries. Novel materials for conversion-type cathodes and alloying-type anodes offer an opportunity to double energy stored in LIBs, reduce their cost by the same factor, and improve cell safety. Conventional separators suffer from poor thermal stability, limited mechanical strength in tension and compression, relatively large minimum thickness of 6 micron (typically 10-25 micron for safer versions used in electric vehicle (EV) LIBs) and relatively high ionic resistance, undesired for ultra-fast charging. Ceramic and ceramic-composite nanofiber-based separators enable one to overcome the current limitations and produce safer LIBs with higher energy density and faster charging abilities. Finally, conventional organic electrolytes suffer from flammability, limited electrochemical stability in contact with anodes and cathodes of high-energy LIBs and undesired chemical and electrochemical reactions with cathode materials that accelerate LIB fading, particularly at elevated temperatures. Several classes of solid electrolytes may offer effective solutions to overcome such drawbacks. In this invited talk I will provide an overview of the activities of our group in these complementary fields and share my understanding of the industrial requirements for the technology adoption and successful commercialization.

A New Lithium‐Ion Conductor LiTaSiO5: Theoretical Prediction, Materials Synthesis, and Ionic Conductivity

AbstractOwing to the nonleakage and incombustibility, solid electrolytes are crucial for solving the safety issues of rechargeable lithium batteries. In this work, a new class of solid electrolyte, acceptor‐doped LiTaSiO5, is designed and synthesized based on the concerted migration mechanism. When Zr4+ is doped to the Ta5+ sites in LiTaSiO5, the high‐energy lattice sites are partly occupied by the introduced lithium ions, and the lithium ions at those sites interact with the lithium ions placed in the low‐energy sites, thereby favoring the concerted motion of lithium ions and lowering the energy barrier for ion transport. Therefore, the concerted migration of lithium ions occurs in Zr‐doped LiTaSiO5, and a 3D lithium‐ion diffusion network is established with quasi‐1D chains connected through interchain channels. The lithium‐ion occupation, as revealed by ab initio calculations, is validated by neutron powder diffraction. Zr‐doped LiTaSiO5 electrolytes are successfully synthesized; Li1.1Ta0.9Zr0.1SiO5 shows a conductivity of 2.97 × 10−5 S cm−1 at 25 °C, about two orders of magnitude higher than that of LiTaSiO5, and it increases to 3.11 × 10−4 S cm−1 at 100 °C. This work demonstrates the power of theory in designing new materials.

Ionic conduction in Li3Na(NH2)4: Study of the material design for the enhancement of ion conductivity in double-cation complex hydrides

Complex hydrides have collected recent attention as a new class of solid electrolytes with potential applications in all-solid-state batteries. To improve ionic conduction in the complex hydrides, multi-cation crystal structure can be attractive. It will allow tuning the cation dynamics via structure modification depending on types and number of additional cations. However, multi-cation crystal structure struggles with the inter-cation scattering among different cations. To address this issue, understanding the conduction mechanisms in the multi-cationic crystals is indispensable. Here, we study cationic conduction in a double-cation (Li and Na) complex hydride Li3Na(NH2)4, which is formed by replacing Li (with Na) from specific lattice site of LiNH2 without altering the crystal symmetry. The nuclear magnetic resonance (NMR) measurements found that Li3Na(NH2)4 is a Li-ion conductor with negligibly small Na-ion conduction. This finding is critically important to elucidate Li-ion conduction mechanism in Li3Na(NH2)4. Enhanced Li-ion conduction in Li3Na(NH2)4 is achieved by (a) suppressing diffusion of Na cation trapped at the strategically located 2c lattice sites under deep potential well; and (b) by increasing the Li defect concentration influenced by the larger volume of the Li metastable sites due to Na substitution into LiNH2. Our study will provide the design principle for multi-cation complex hydrides, and accelerate development of superior solid electrolytes for all-solid-state batteries.

Ammonia for Proton Conducting Medium in Metal-Organic Frameowkrs

Proton transport is essential and critical in a biological system and electrochemical devices. In particular, the fundamental understanding of proton conduction mechanism in conducting medium is important to design the efficient proton conductor. The overwhelming majority of proton conducting medium is water (H2O) which was intensively investigated because water can form the efficient hydrogen bonding networks by symmetric two proton donor and two acceptor sites resulting in degenerated proton conduction system (H3O++H2O ⇔ H2O+H3O+). In this point of view, we believe that ammonia (NH3) can be a next promising conducting medium due to its similar molecular system to water. Specifically, it shows a small molecular size (2.60 Å), three proton donor sites/ one acceptor site, and degenerated proton conduction system (NH4 ++NH3 ⇔ NH3+NH4 +). Considering the fluid phase of NH3, a confined environment should be required to achieve NH3 proton conductor. The porous crystalline metal-organic frameworks (MOFs), tunable solid, are emerging as a new class of solid electrolyte because of a considerable porosity and versatile sorptivity. In particular, the pore of MOFs is a suitable platform to confine the guest molecules. In addition, a simultaneous proton donation from framework to NH3 can induce the conjugated acid-base system in the pores. Here, we show, for the first time, proton conductivity through the simultaneously confined NH3 in MOFs by NH3 adsorption. We choose highly stable Al-based MOFs consisting of one-dimensional channel and MO4(OH)2 secondary building units (SBUs) interconnected by dicarboxylate groups. Fuethermore, we can tune the pore environment by using the different fuctionla groups of ligand. We found cooperative ammonia adsorption with simultaneous ammonium formation and the highly enhanced proton conductivity as NH3 pressure increases. Tthe structure analysis of MOFs incorporating NH3 by Rietveld refinement and dynamic motion study of confined NH3 by 2H solide-state NMR help to understand proton conduction mechanism. These results clearly support the Grotthuss mechanism not seen in bulk NH3 system. We believe that this research may provide a design strategy for material using NH3 as a conducting media as well as an energy carrier.

Highly Ion-Conducting, Reversibly Stretchable, and Ultra-Durable Double-Networked Ionogels for Flexible Supercapacitor

Flexible energy storage devices perform well under normal condition and their performance merits are well understood. However, energy storage under extreme conditions is still a big challenge because of electrolyte degradation and separator instability for the application such as an electrical vehicle, oil, solar energy storage, aerospace and military. Wet gels such as hydro- and organogels are mechanically strong yet brittle. Among functional gels, gel electrolytes are considered to resolve critical challenges of liquid and solid electrolytes, but they also have the property trade-offs between ion transporting and mechanical properties, as well as between strength and toughness. The performance degradation and safety issue of electrolytes prohibit flexible energy storage from operating under mechanically, thermally and electrochemically extreme conditions. Here, we report a new class of solid electrolyte, “Double Crosslinked Ionogel” based on double network concept. The tailor made ionogel electrolyte/separator structure was prepared by synthesizing double network gel from complimentary polymers and by combining it with room temperature ionic liquid. The unique structure of double crosslinked ionogel electrolyte was characterized by solid-state 13C CP-MAS NMR and FT-IR spectroscopies. Dual crosslinked polymer structure provide greater stretchability (strain ~250%) and high mechanical strength (3 MPa) to the electrolyte. At the same time presence of high amount of ionic liquid results (~60 wt%) in enhanced electrochemical performance i.e. Potential window (~2V), Maximum energy density (~40 Wh kg-1) and Ionic conductivity (~1.8 mS cm-1 at Room temp). With rGO electrodes and prepared ionogel electrolyte/separator, the supercapacitor device shows stable performance up to 180°C with good cyclic stability. High temperature promotes faster ion transport and hence results in enhanced performance in terms of rate capability (≈40%) and maximum device capacitance (≈ 32 F g-1). There was very little performance attenuation observed even under extreme mechanical and thermal stress. The device retains around ~90 % of its initial capacitance even after 100000 of cycles at 150 °C and capable of delivering required energy and power at high temperature.

Spark Plasma Sintering Study on the Super Ionic Glass Ceramic Conductor: Li7P3S11

Solid-state electrolytes that can perform on par with conventional liquid electrolytes are highly sought after for use in all solid-state batteries. An all solid-state battery promises to operate without the possibility of catastrophic failure and have substantially longer self-life than conventional batteries. The Li7P3S11 glass-ceramic is one class of solid electrolytes that could meet the sought after power and reliable performances. We demonstrate a rapid synthesis and densification of the supersonic conductor electrolyte Li7P3S11via spark plasma sintering (SPS) technique. Dense solid-state electrolytes have been formed with a room temperature ionic conductivity is comparable to conventional liquid electrolyte. Hayashi, A., Ishikawa, Y., Hama, S., Minami, T. & Tatsumisago, M. Fast Lithium-Ion Conducting Glass-Ceramics in the System Li[sub 2]S-SiS[sub 2]-P[sub 2]S[sub 5]. Electrochem. Solid-State Lett. 6, A47 (2003).Seino, Y., Ota, T. & Takada, K. A sulphide lithium super ion conductor is superior to liquid ion conductors for use in rechargeable batteries. Energy … 7, 627 (2014).Hayashi, A., Minami, K., Mizuno, F. & Tatsumisago, M. Formation of Li+ superionic crystals from the Li 2S-P2S5 melt-quenched glasses. J. Mater. Sci. 43, 1885–1889 (2008).Minami, K., Hayashi, A. & Tatsumisago, M. Crystallization Process for Superionic Li7P3S11 Glass-Ceramic Electrolytes. J. Am. Ceram. Soc. 94, 1779–1783 (2011).Minami, K., Hayashi, A. & Tatsumisago, M. Crystallization Process for Superionic Li7P3S11 Glass-Ceramic Electrolytes. J. Am. Ceram. Soc. 94, 1779–1783 (2011).Eom, M., Kim, J., Noh, S. & Shin, D. Crystallization kinetics of Li2S–P2S5 solid electrolyte and its effect on electrochemical performance. J. Power Sources 284, 44–48 (2015). Acknowledgments This work was supported by the National Science Foundation under grant number ACI-1053575.

“Liquid-in-Solid” and “Solid-in-Liquid” Electrolytes with High Rate Capacity and Long Cycling Life for Lithium-Ion Batteries

Herein we present a new class of ionogel electrolyte for lithium-ion batteries, which can be prepared in either “liquid-in-solid” or “solid-in-liquid” form. The electrolytes are prepared by a nonaqueous self-assembly sol–gel process, in which ionic liquid electrolyte is immobilized within an inorganic gel. These electrolytes were found to exhibit high ionic conductivity, low electronic conductivity, and good thermal and mechanical stability. The inorganic gels weaken the interaction of anions and cations and thereby improve lithium salt dissociation and enhance transport of Li+. Also, the electrolytes are stable: no spontaneous phase separation occurs after 1 year of storage. In addition, their synthesis and shaping are very easy and cheap and form a new class of solid electrolytes, which offer exciting opportunities for preparation of in situ solid-state lithium-ion batteries. Cells with LiFePO4 cathodes and ionogel electrolyte attained a capacity of 150 mAh/g for more than 300 cycles, and even at the 2C...

Superionic Conductivity in Lithium-Rich Anti-Perovskites

Lithium ion batteries have shown great promise in electrical energy storage with enhanced energy density, power capacity, charge-discharge rates, and cycling lifetimes. However common fluid electrolytes consisting of lithium salts dissolved in solvents are toxic, corrosive, or flammable. Solid electrolytes with superionic conductivity can avoid those shortcomings and work with a metallic lithium anode, thereby allowing much higher energy densities. Here we present a novel class of solid electrolytes with three-dimensional conducting pathways based on lithium-rich anti-perovskites (LiRAP) with ionic conductivity of σ > 10(-3) S/cm at room temperature and activation energy of 0.2-0.3 eV. As temperature approaches the melting point, the ionic conductivity of the anti-perovskites increases to advanced superionic conductivity of σ > 10(-2) S/cm and beyond. The new crystalline materials can be readily manipulated via chemical, electronic, and structural means to boost ionic transport and serve as high-performance solid electrolytes for superionic Li(+) conduction in electrochemistry applications.

A wide-ranging review on Nasicon type materials

Nasicons (sodium super ion conductors) are a class of solid electrolytes. Their structure, compositional diversity, evolution, and applications are reviewed. A wide range of materials is considered based on crystalline and glassy Nasicon compositions.